Front Rail Configuration for the Front Structure of a Vehicle

ABSTRACT

A front structure for a vehicle is provided that includes a pair of front rails (i.e., front left hand rail and front right hand rail) spaced apart in a widthwise direction with each rail extending lengthwise and mechanically coupled to the vehicle&#39;s bumper and a torque box. Each front rail is comprised of a polygonal-shaped upper hollow channel and a polygonal-shaped lower hollow channel, where the upper and lower channels share a common wall.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims benefit of the filing date of U.S.Provisional Patent Application Ser. No. 61/430,622, filed Jan. 7, 2011,the disclosure of which is incorporated herein by reference for any andall purposes.

FIELD OF THE INVENTION

The present invention relates generally to vehicle structures and, moreparticularly, to front-end vehicle structures that provide enhanced loaddistribution and occupant safety.

BACKGROUND OF THE INVENTION

Modern vehicles use a variety of structures to protect the vehicle'soccupants during a crash. Some of these structures are used to controlthe transmission of the crash energy to the passenger compartment whileother structures, such as seat belts, head restraints, and air bags, areintended to restrain passenger movement during a crash, therebypreventing the passengers from hurting themselves as their bodies reactto the crash forces. In addition to reducing the potential for personalinjuries, many vehicle crash structures are also designed to minimizevehicle damage and simplify post-crash repairs.

A variety of different approaches and structures have been used toabsorb and control the transmission of crash energy into the vehicle. Asthe bumper is typically the first vehicle structure to be impactedduring a crash, many crash structures attempt to absorb as much energyas possible in the bumper itself, thus minimizing the energy that istransmitted into the vehicle. For example, U.S. Pat. No. 4,018,466discloses a bumper assembly in which the bumper is comprised of a hollowbeam that houses a plurality of shock absorbing cellular blocks. Theshock absorbing cellular blocks are inserted into pocket-like sectionsof the bumper. In an alternate shock-absorbing bumper, disclosed in U.S.Pat. No. 6,000,738, the bumper includes an outer wall disposed toreceive the crash force, an inner wall that is coupled to the vehiclestructure and four walls that connect the inner and outer bumper walls.During a car crash, the four connecting walls are designed to bend at acontrolled rate, thereby absorbing crash energy.

While crash energy may be absorbed in the bumper, large impact crashestypically require the use of other energy absorbing structures. Forexample, in a conventional vehicle the bumpers are often coupled to thevehicle by one or more crash boxes that are designed to collapse duringa crash, thereby absorbing crash energy. U.S. Pat. No. 7,290,811discloses one design for a crash box in which two overlapping andinterconnected sheet metal shells form the crash box. The crash box isbolted to the bumper cross-member using at least one bolt that extendsin a vertical direction through the overlap zone of the structure. U.S.Pat. No. 7,533,913 discloses an alternate crash box design using innerand outer curved members which extend in the longitudinal direction ofthe vehicle. The inner member includes a plurality of bead-shapedprotrusions that are intended to cause longitudinal compressingdeformation of this member in a low-speed collision, thereby helping todirect the striking energy created by the collision away from the insideof the vehicle.

In addition to designing the front structure of a vehicle to absorb anddistribute the impact loads generated during a crash, it is criticalthat these same structures also achieve the desired level of vehiclestability and maneuverability, preferably in a lightweight structurethat minimizes its impact on the vehicle's MPG or MPG_(equivalent). Oneattempt at balancing these goals is disclosed in U.S. Patent ApplicationPublication No. 2004/0056515, published 25 Mar. 2004, in which arelatively simple front structure is provided that is designed to berigid and, due to the elimination of various reinforcing members,lightweight.

It is therefore an object of the present invention to provide a vehiclefront structure that achieves improved performance in terms of frontimpact load distribution, structure weight, vehicle frame rigidity, andvehicle maneuverability.

SUMMARY OF THE INVENTION

The present invention provides a front rail structure for a vehicle, thefront rail structure including a pair of front rails (i.e., front lefthand rail and front right hand rail) spaced apart in a widthwisedirection with each rail extending lengthwise, where one end portion ofeach rail is mechanically coupled to the vehicle's bumper and the otherend portion of each rail is mechanically coupled to a torque box (i.e.,left hand torque box and right hand torque box), and where each rail iscomprised of a polygonal-shaped upper hollow channel and apolygonal-shaped lower hollow channel, and where the upper and lowerchannels share a common wall. The structure may include a left handrocker panel coupled to the left hand torque box and a right hand rockerpanel coupled to the right hand torque box, along with a battery packenclosure mounted between and mechanically coupled to the left and righthand rocker panels. The battery pack enclosure, which may besubstantially airtight and fabricated from aluminum, an aluminum alloyor steel, includes a top panel, a bottom panel and a plurality of sidemembers. The battery pack enclosure may also include a plurality ofbattery pack cross-members that traverse the distance between enclosureside members adjacent to the left and right hand rocker panels, and thatsegregate the batteries into groups of batteries. The left hand andright hand front rails may be non-parallel, e.g., offset by at least 2.5degrees from one another, and fabricated from an aluminum extrusion, analuminum alloy extrusion or a steel extrusion. The left hand and righthand front rails may each have a cross-sectional height at least 2times, and preferably at least 2.5 times, the cross-sectional width ofeach rail. The polygonal-shaped upper and lower hollow channels of thefront rails may utilize a regular or non-regular octagon-shapedstructure, or a regular or non-regular hexagon-shaped structure. Thefront structure of the vehicle may include a pair of crush cans, whereone crush can is interposed between the end portion of each rail and thevehicle's bumper. The front structure of the vehicle may include a frontvehicle module with a pair of mounting plates, where a front vehiclemodule mounting plate is interposed between the end portion of each railand the vehicle's bumper.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a perspective view of a portion of a vehicle body andframe with the battery pack separated from the structure;

FIG. 2 provides a perspective view of a vehicle's undercarriage with thebattery pack of FIG. 1 incorporated into the vehicle structure;

FIG. 3 provides a simplified bottom view of an electric vehicle'sundercarriage with the battery pack of FIG. 1 incorporated into thevehicle structure;

FIG. 4 provides a perspective view of a battery pack to rocker panelassembly;

FIG. 5 provides a perspective view of the battery pack shown in FIGS.1-4;

FIG. 6 provides a perspective view of the battery pack shown in FIGS.1-5, with the top panel removed;

FIG. 7 provides a perspective view of the primary components associatedwith the primary and secondary front impact load paths in accordancewith one aspect of the invention;

FIG. 8 provides a perspective view similar to that shown in FIG. 7, withseveral battery enclosure cover panels removed so that the battery packenclosure is clearly visible;

FIG. 9 provides a perspective, detailed view of a front rail to bumpermounting plate;

FIG. 10 provides a cross-sectional view of a section of a front railattached to the bumper mounting plate, this view taken through the planecontaining the mounting rivets;

FIG. 11 provides a perspective view of a bumper mounting plate attachedto a front rail;

FIG. 12 provides a perspective view of a crush can and bumper modulecoupled to a front rail;

FIG. 13 provides a perspective view similar to that provided in FIG. 12,with the addition of the primary bumper coupled to the crush can;

FIG. 14 provides a perspective view of the mechanical coupling of thefront rails to the side sills via a pair of swept torque boxes;

FIG. 15 provides a top view of the assembly shown in FIG. 14;

FIG. 16 provides a side view of the assembly shown in FIG. 14;

FIG. 17 provides a detailed, perspective view of the front rail/torquebox assembly shown in FIGS. 14-16;

FIG. 18 provides a perspective view of an exemplary rail reinforcementmember, this reinforcement member being configured for the left handfront rail;

FIG. 19 provides an end view of rail reinforcement member within a frontrail;

FIG. 20 provides a perspective view of a front rail, shown in phantom,which includes the internally mounted, rail reinforcement member;

FIG. 21 provides a cross-sectional side view taken along a longitudinalplane of a front rail with an integral reinforcement member;

FIG. 22 provides a cross-sectional top down view taken along alongitudinal plane of the front rail with integral reinforcement membershown in FIG. 21, this reinforcement member being configured for theright hand front rail;

FIG. 23 provides a cross-sectional top down view taken along alongitudinal plane of the front rail with integral reinforcement membershown in FIG. 21, this reinforcement member being configured for theright hand front rail;

FIG. 24 provides a cross-sectional end view of the front rail withintegral reinforcement member taken along a plane that intersects theprimary sub-frame mount;

FIG. 25A provides a side view of the assembly shown in FIGS. 7 and 8;

FIG. 25B provides a side view similar to that provided in FIG. 25A, withthe lower load path removed;

FIG. 25C provides a side view similar to that provided in FIG. 25A, withthe upper load path removed;

FIG. 26A provides a top view of the assembly shown in FIG. 7;

FIG. 26B provides a top view similar to that provided in FIG. 26A, withthe lower load path removed; and

FIG. 26C provides a top view similar to that provided in FIG. 26A, withthe upper load path removed.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

In the following text, the terms “battery”, “cell”, and “battery cell”may be used interchangeably and may refer to any of a variety ofdifferent cell types, chemistries and configurations including, but notlimited to, lithium ion (e.g., lithium iron phosphate, lithium cobaltoxide, other lithium metal oxides, etc.), lithium ion polymer, nickelmetal hydride, nickel cadmium, nickel hydrogen, nickel zinc, silverzinc, or other battery type/configuration. The term “battery pack” asused herein refers to multiple individual batteries electricallyinterconnected to achieve the desired voltage and capacity for aparticular application. The batteries of the battery pack are containedwithin a single piece or multi-piece housing referred to herein as abattery pack enclosure, and often referred to herein as simply the“battery pack”. The term “electric vehicle” as used herein refers toeither an all-electric vehicle, also referred to as an EV, a plug-inhybrid vehicles, also referred to as a PHEV, or a hybrid vehicle, alsoreferred to as a HEV, a hybrid vehicle utilizing multiple propulsionsources one of which is an electric drive system.

The present invention provides a number of vehicle structures andassemblies which, used alone or in combination, provide superior vehicleperformance. Although these structures and assemblies may be used inboth electric vehicles and conventional vehicles, in general they havebeen optimized to achieve peak performance in an electric vehicle, andin particular in an electric vehicle in which a large battery packenclosure is integrated into the vehicle's frame as illustrated in FIGS.1-3. As shown, battery pack enclosure 101 is mounted to theundercarriage of a vehicle 100 and attached to the body sub-frame aswell as the front and rear suspension sub-frames. Preferably and asshown, battery pack enclosure 101 transverses the width of the vehicle,i.e., from rocker panel to rocker panel, and extends between the frontsuspension 201 and the rear suspension 203. In the illustratedembodiment, battery pack 101 is approximately 2.7 meters long and 1.5meters wide. The thickness of battery pack enclosure 101 varies fromapproximately 0.1 meters to 0.18 meters, the thicker dimensioncorresponding to those portions of the battery pack in which batterymodules are positioned one on top of another.

As noted above, preferably battery pack 101 is configured to transversethe width of the vehicle and be coupled to the rocker panels located oneither side of the vehicle. FIG. 4 illustrates an exemplary techniquefor attaching battery pack 101 to rocker panel 401, this figure showingthe location of battery pack 101 under vehicle floor panel 403.Preferably rocker 401 is extruded, for example using an aluminum oraluminum alloy extrusion as described in detail in co-pending U.S.patent application Ser. No. 13/308,206, filed 30 Nov. 2011, and attachedto the battery pack as described in co-pending U.S. patent applicationSer. No. 13/308,300, filed 30 November 2011, the disclosures of whichare incorporated herein for any and all purposes. In general and asillustrated for the preferred embodiment, battery pack enclosure 101includes side members 405 that include a mounting flange. In theillustrated embodiment, the mounting flange is an extended mountingregion 407 that is positioned under rocker 401. Region 407 is perforatedin order to allow passage of a plurality of mounting bolts 409. Mountingbolts 409, in combination with nuts 411, mechanically couple extendedregion 407 of battery pack 101 to rocker 401. To simplify assembly,channel nuts 411 are held in place during vehicle assembly using achannel nut retainer 413. Retainer 413 is positioned within rocker 401using internal feature 415, thereby simplifying vehicle assembly andreducing manufacturing costs. It will be understood that othertechniques may be used to mount the battery pack under the vehicle'sfloor panel.

FIG. 5 provides a perspective view of battery pack enclosure 101 withthe top enclosure panel 501 in place, panel 501 preferably providing asubstantially airtight seal. Hollow side structural elements 405 arealso visible, members 405 preferably including an extended region orflange 407 that is used to mechanically and thermally couple the sidemembers 405 to the vehicle structure (not shown in this figure). FIG. 6shows battery pack 101 with top member 501 removed, this view showingcross-members 601. The number of cross-members is based on the number ofcells/cell modules that are to be contained within the battery packwhile the dimensions of individual cross-members are based on thedesired structural characteristics of the battery pack enclosure.Preferably battery pack side members 405, including extended region 407,battery pack top panel 501 and battery pack bottom panel 603 are eachfabricated from a light weight metal, such as aluminum or an aluminumalloy, although other materials such as steel may be used for some orall of the battery pack components. Bottom panel 603 may be welded,brazed, soldered, bonded or otherwise attached to side members 405, withthe resultant joint between panel 603 and member 405 preferably beingsubstantially air-tight as well as being strong enough to allow bottompanel 603 to support the batteries contained within the pack. Top panel501 is typically attached to member 405 using bolts or similar means,thus simplifying battery replacement as well as allowing batteryinterconnects, battery pack components, cooling system components andother battery pack components to be repaired and/or replaced.

Cross-members 601 provide several benefits. First, members 601 providemechanical and structural strength and rigidity to the battery packenclosure as well as to the vehicle to which the battery pack isattached. Second, members 601 help to segregate thermal events byproviding a thermal barrier between groups of cells as well asminimizing gas flow between sections 605, sections 605 being defined bythe cross-members, side members 405, top member 501 and bottom member603. By segregating thermal events within smaller groups of cells,thermal runaway propagation is limited as is the potential for batterypack damage.

FIGS. 7 and 8 provide perspective views of the primary components of theprimary and secondary load paths associated with the preferredembodiment of vehicle 100. The primary difference between FIGS. 7 and 8is that in FIG. 7 battery enclosure 101 is covered by several panels701, while in FIG. 7 battery pack enclosure 101 is clearly visible. Bothviews clearly show the front module 703, as well as the primary bumper705 and a secondary bumper 707. As shown, secondary bumper 707 ispositioned much lower to the ground than primary bumper 705, thusreducing the severity of injuries if the vehicle is involved in anaccident with a pedestrian.

FIGS. 9-13 illustrate a preferred approach to mechanically coupling theprimary bumper 705 to the front rails 709. In the preferred embodimentand as illustrated in the accompanying figures, the vehicle side rails709, which extend in a longitudinal direction and are located onopposite traverse sides of the vehicle as shown, are comprised of a pairof multi-walled channels that share a common wall. In at least someembodiments, and as shown, each channel is a non-regular, octagon-shapedstructure. In at least some other embodiments, each channel is aregular, octagon-shaped structure; alternately, a regular or non-regularhexagon-shaped structure. The multi-walled channel shape providesstrength and rigidity in a relatively low-weight structure. Vehicle siderails 709 are preferably fabricated from aluminum or an aluminum alloyusing an extrusion process, although other materials and fabricationprocesses may be used. In this embodiment, the double-octagon shapedstructure has a height of approximately 200 millimeters, a width ofapproximately 76 millimeters, and a wall thickness of between 2-4millimeters while in at least one vehicle configuration, the length ofeach front rail 709 is approximately 800 millimeters taken at itslongest point. The tall cross-sectional height of the front rails (i.e.,preferably at least 2 times the cross-sectional width of the frontrails, more preferably at least 2.5 times the cross-sectional width ofthe front rails) reduces the distance between the neutral axis of therail cross-section and the neutral axis of side sills 401, thus helpingto balance the collapse mode of the front vehicle structure.

In the illustrated embodiment, interposed between each front rail 709and bumper 705 is a crush can 1201, crush can 1201 preferably beingfabricated from steel although other materials (e.g., aluminum, aluminumalloys, etc.) may be used. Crush cans 1201 are designed to collapseduring a crash, thus absorbing some or all of the load energy, dependingupon the impact force, imparted to the bumper by the collision. Thecrush cans are attached to the front rails using a pair of mountingflanges, the first flange 1203 corresponding to crush can 1201 and thesecond, complementary flange 901 corresponding to a bumper mountingplate 711. Mounting plate 711 is preferably fabricated from aluminum,for example using a high pressure die casting technique, although othermaterials (e.g., aluminum alloy, steel, etc.) and fabrication techniquesmay be used. A third flange 1301, only partially visible in thesefigures, is used to attach bumper 705 to the front of each crush can1201. In this embodiment, each crush can is aligned with the upperchannel 1101 of rails 709, thus achieving a direct transfer of frontimpact loads from bumper 705 to the top rail channel 1101. Lower railchannel 1103 adds to the load carrying capabilities of the each frontrail 709 while lowering the neutral axis of the rail section.Additionally, due to the high stiffness of bumper mounting plate 711,impact loads are effectively transferred not only to upper channel 1101of rail 709, but also to lower channel 1103, thus insuring a stableaxial collapse of the rail tip.

Flanges 1203 and 901 are bolted together using a plurality of bolts1205. One benefit of using mounting flanges or similar means to hold thecrush structures in place is that in the case of a minor collision it isoften possible to simply remove and replace the crush structureassemblies, along with bumper 705, without having to repair the primaryvehicle structure (e.g., front side rails). In the illustratedconfiguration, interposed between mounting flanges 901 and 1203 is amounting surface 1207 of front module 703.

As shown in FIG. 9, in addition to mounting flange 901, bumper mountingplate 711 includes a pair of sleeves 903. Sleeves 903 are configured tofit within the ends of upper channel 1101 and lower channel 1103 offront rail 709 as illustrated in FIGS. 10 and 11. Mounting plate 711 ispreferably attached to rail 709 with a plurality of rivets 1001 asshown. In at least one embodiment, a structural adhesive is also usedbetween the front rails and the bumper mounting plate.

FIGS. 14-17 illustrate the mechanical coupling of front rails 709 torocker panels 401, also referred to herein as side sills or simply asrockers. As illustrated, front rails 709 are attached to rockers 401using a pair of swept (i.e., curvilinear) torque boxes 1401, thecurvilinear (i.e., swept) shape helping to redirect impact loads outwardto rocker panels 401. In this embodiment, each torque box is comprisedof three members 1701-1703 that are assembled using MIG welding, eitheralone or in combination with rivets. Primary torque box member 1701 isheavily ribbed as illustrated (see, for example, ribs 1705). Preferablyprimary torque box member 1701, and more preferably all three members1701-1703, are fabricated from aluminum, for example using a highpressure die casting technique, although other materials (e.g., aluminumalloy, steel, etc.) and fabrication techniques may be used. Members 1702and 1703, while coupled to the primary torque box member 1701, areactually outer and inner rail extensions, respectively. Also shown inFIG. 17 is a cross-member 1707 that is welded between, and to, the pairof front torque boxes 1701.

In the preferred embodiment, each torque box 1401 is welded to thecorresponding front rail 709 and to the corresponding sill 401. The heataffected zone at the weld joint between the torque box and the frontrail, along with the angle of the front rail rear tip section and thusthe angle of the joint, helps to initiate controlled bending of the railsystem during a front vehicle collision. In the illustrated embodiment,the angle between the horizontal plane and the end surface of rail 709,measured from the bottom surface of the rail, is in the range of 100 to140 degrees, preferably in the range of 110 to 130 degrees, morepreferably in the range of 115 to 125 degrees, and still more preferablyapproximately 120 degrees. Additionally, and as illustrated in FIG. 15,in the preferred embodiment the front rails are not parallel, ratherrails 709 are offset by approximately 2.5 degrees thus providingimproved performance during a vehicle collision.

In order to further tune the response of the front vehicle structures tofront vehicle impacts, in at least one preferred embodiment a front railreinforcement member is mechanically coupled to each of the front rails.FIG. 18 provides a perspective view of an exemplary rail reinforcementmember 1800, the design of which allows the member to be inserted into afront rail. FIG. 19 provides an end view of rail reinforcement member1800 within a front rail 709. FIG. 20 provides a perspective view of afront rail 709, shown in phantom, which includes the internally mounted,rail reinforcement member 1800. FIG. 21 provides a cross-sectional sideview taken along longitudinal plane A-A of a front rail 709 withintegrated reinforcement member 1800. FIG. 22 provides a cross-sectionaltop down view taken along longitudinal plane B-B of the front rail withintegral reinforcement member shown in FIG. 21. FIG. 23 provides across-sectional top down view taken along longitudinal plane C-C of thefront rail with integral reinforcement member shown in FIG. 21. FIG. 24provides a cross-sectional end view taken along a plane that intersectsthe primary sub-frame mount.

In a preferred embodiment, each rail reinforcement member is comprisedof an upper member 1801, configured to fit within upper rail channel1101, and a lower member 1803, configured to fit within lower railchannel 1103. Upper member 1801 and lower member 1803 are preferablyfabricated using an extrusion process and formed of aluminum or analuminum alloy, although other materials (e.g., steel) and fabricationtechniques may be used. Upper member 1801 is mechanically coupled to theupper rail channel 1101 with a plurality of rivets 1901. Similarly,lower member 1803 is mechanically coupled to the lower rail channel 1103with a plurality of rivets 1903. Additionally, lower member 1803 iscoupled to the vehicle sub-frame structure (e.g., frame members 713shown in FIGS. 7 and 8) using a plurality of sub-frame mounts (e.g.,mounts 1804-1807). It will be appreciated that by coupling lower member1803 to the sub-frame, rail 709 into which the reinforcement member isintegrated is also coupled to the vehicle sub-frame via the sub-framemounts 1804-1807.

In the illustrated and preferred embodiment, at least one of thesub-frame mounts (e.g., mount 1807) extends through both upperreinforcement member 1801 and lower reinforcement member 1803. Sub-framemount 1807 is coupled to upper reinforcement member 1801 with nut 2101.In addition to coupling both the upper and lower reinforcement membersto the vehicle's sub-frame structure, mount 1807 also insures that theupper and lower reinforcement members are aligned.

The rail reinforcement members, i.e., members 1800, are used to controlthe way in which the vehicle's front structure reacts to front impacts,i.e., those arising from vehicle collisions. In particular, if theimpact load on bumper 705 is large enough to transfer a significantforce through the crush cans 1201 (assuming the use of crush cans) andinto the front rails, the reinforcement members define the reaction ofthe rails. As a result of the inclusion of reinforcement members withinthe front rails, as the impact load is transferred into the railsinitially the front zone (zone 1 in FIGS. 22 and 23) will axiallycollapse. The front sections of the rails will also tend to bendslightly inward, i.e., towards the center of the vehicle. Note that zone1 corresponds to the region in front of the reinforcement member 1800.

If the impact force is large enough, in addition to causing the collapseof the forward section of the rails, the impact force will cause themiddle section of the rails to bend, preferably bending in a horizontalplane. In the illustrated configuration, due to the shape of thefeatures in zones 2 and 3 of the reinforcement members, the middle railsections will bend outwardly, away from the vehicle centerline. Bendinitiation is promoted by the features within zone 2, specifically theangled leading edge 1809 of upper member 1801, and the cutouts 1811/1812on lower member 1803. Note that to promote bending in the desireddirection, cutout 1812 is smaller than cutout 1811. Additionally, edge2301/2302 is angled, with the angle of edge 2301/2302 being similar to,or the same as, the angle of edge 1809. Outward bending within ahorizontal plane is also aided by the features within zone 3,specifically notch 1813 on the interior side of the upper reinforcementmember 1801 (relative to the vehicle) and a similar notch 1815 on theinterior side of the lower reinforcement member 1803. Bending within ahorizontal plane is especially aided by aligning notches 1813 and 1815and using front rails with a relatively tall cross-section. Bendingwithin zone 4 is promoted by the elimination of the reinforcement member1800 within the rail, and the heat affected zone at the weld jointbetween the swept torque boxes 1401 and the front rails 709. It will beappreciated that other features may be included within the reinforcementmembers in order to promote different reactions to front impact loads,e.g., inward bending of the mid-rail section, out-of-plane bending ofthe rails, different size or elimination of the axial collapse region atthe front tip of the rails, etc.

As described above and illustrated in FIGS. 7 and 8, the preferredembodiment of the vehicle front structure includes a primary bumper 705and a secondary bumper 707, with secondary bumper 707 being positionedmuch lower to the ground than the primary bumper 705. These two bumpersare coupled to the vehicle using two different sets of structures. As aresult, this configuration provides two different pathways that work inparallel to absorb and distribute impact loads arising from vehiclefrontal collisions.

In general and especially given the height of the bumpers, bumper 705provides the primary load path during a collision. However, except invery minor collisions, lower bumper 707 will also be impacted, therebyproviding a secondary load path that helps to absorb and distribute theimpact energy and minimize the effects of the impact on the passengercabin and the vehicle's occupants. In the following description and thereferenced figures, it should be understood that in a typical andpreferred vehicle configuration, front module 703 is simply attached tothe upper and lower load structures but may have minimal effect on theabsorption and distribution of impact loads. For example and asdescribed above, module 703 simply includes a mounting flange that, inthe illustrated embodiment, is positioned between the crush can mountingflange 1203 and the mounting flange of the front rail mounting plate711. As the module mounting flange has virtually no effect on thetransfer of impact energy through bumper 705 and crush cans 1201 andinto the front rails 709, this module has little effect on loadabsorption and distribution.

FIGS. 25A-25C and 26A-26C illustrate the two different impact load pathsof the preferred embodiment with FIGS. 25A-25C and FIGS. 26A-26Cproviding side and top views, respectively, of the primary structuresinvolved in each load path. In particular, FIGS. 25A and 26A illustrateboth impact load paths; FIGS. 25B and 26B illustrate the primary impactload path which is coupled to the primary bumper 705; and FIGS. 25C and26C illustrate the secondary load path which is coupled to the secondarybumper 707.

As illustrated, primary bumper 705 transfers impact load energy throughthe front rails 709 and the swept torque boxes 1401 into side sills 401.Preferably a battery pack enclosure 101 is interposed between, andattached to, the side sills as described and illustrated above, therebyproviding additional strength and rigidity to the side sill. In such aconfiguration, impact energy arising from large frontal collisions isalso absorbed and distributed into the battery pack enclosure. In thepreferred embodiment, crush cans 1201 are interposed between primarybumper 705 and front rails 709 and reinforcement members 1800 are usedwithin front rails 709 to aid in front impact load absorption anddistribution.

In the secondary load path, load energy arising from an impact onsecondary bumper 707 is transferred into the sub-frame members 713.Although crush cans may be added between bumper 707 and sub-framemembers 713, in the preferred embodiment bumper 707 is directly coupledto sub-frame members 713 without the inclusion of crush cans. In thepreferred and illustrated embodiment, sub-frame members 713 are attachedto the front structure 503 of battery pack enclosure 101 (see, forexample, FIG. 5), thus allowing impact energy passing through sub-framesmembers 713 to be absorbed and distributed by the battery packenclosure.

It should be understood that identical element symbols used on multiplefigures refer to the same component, or components of equalfunctionality. Additionally, the accompanying figures are only meant toillustrate, not limit, the scope of the invention and should not beconsidered to be to scale.

Systems and methods have been described in general terms as an aid tounderstanding details of the invention. In some instances, well-knownstructures, materials, and/or operations have not been specificallyshown or described in detail to avoid obscuring aspects of theinvention. In other instances, specific details have been given in orderto provide a thorough understanding of the invention. One skilled in therelevant art will recognize that the invention may be embodied in otherspecific forms, for example to adapt to a particular system or apparatusor situation or material or component, without departing from the spiritor essential characteristics thereof. Therefore the disclosures anddescriptions herein are intended to be illustrative, but not limiting,of the scope of the invention which is set forth in the followingclaims.

1. A front structure of a vehicle comprising a pair of front rails,wherein said pair of front rails are spaced apart in a widthwisedirection relative to said vehicle, wherein each of said pair of frontrails extend in a lengthwise direction relative to said vehicle, whereinsaid pair of front rails comprise a front left hand rail and a frontright hand rail, wherein a first end portion of said front left handrail is mechanically coupled to a left portion of a vehicle bumper and afirst end portion of said front right hand rail is mechanically coupledto a right portion of said vehicle bumper, wherein a second end portionof said front left hand rail distal from said first end portion of saidfront left hand rail is mechanically coupled to a left hand torque box,wherein a second end portion of said front right hand rail distal fromsaid first end portion of said front right hand rail is mechanicallycoupled to a right hand torque box, wherein each of said pair of frontrails is comprised of a polygonal-shaped upper hollow channel and apolygonal-shaped lower hollow channel, and wherein said polygonal-shapedupper hollow channel and said polygonal-shaped lower hollow channelshare a common wall.
 2. The front structure of claim 1, furthercomprising a left hand rocker panel and a right hand rocker panel,wherein said left hand torque box is mechanically coupled to said lefthand rocker panel, and wherein said right hand torque box ismechanically coupled to said right hand rocker panel.
 3. The frontstructure of claim 2, further comprising a battery pack enclosuremounted under said vehicle, said battery pack enclosure comprising anenclosure top panel, an enclosure bottom panel, and a plurality ofenclosure side members, wherein said battery pack enclosure isconfigured to hold a plurality of batteries, said battery pack enclosuremounted between and mechanically coupled to said left hand rocker paneland said right hand rocker panel, wherein said battery pack enclosure ismounted under a passenger cabin floor panel, wherein said battery packenclosure further comprises a plurality of battery pack cross-membersintegrated into said battery pack enclosure, wherein each of saidplurality of battery pack cross-members transverses the distance betweena first enclosure side member adjacent to said left hand rocker paneland a second enclosure side member adjacent to said right hand rockerpanel, and wherein said plurality of battery pack cross-memberssegregate said plurality of batteries into groups of batteries.
 4. Thefront structure of claim 3, wherein said plurality of enclosure sidemembers further comprise a mounting flange that is mechanically coupledto said left hand rocker panel and said right hand rocker panel using aplurality of bolts.
 5. The front structure of claim 3, wherein saidenclosure bottom panel is welded, brazed, soldered or bonded to saidplurality of enclosure side members, and wherein said enclosure toppanel is bolted to said plurality of enclosure side members.
 6. Thefront structure of claim 3, wherein said battery pack enclosure issubstantially airtight.
 7. The front structure of claim 3, wherein saidenclosure bottom panel, said enclosure top panel, and said plurality ofenclosure side members are each fabricated from a material selected fromthe group of materials consisting of aluminum, aluminum alloys andsteel.
 8. The front structure of claim 1, wherein said front left handrail is not parallel with said front right hand rail.
 9. The frontstructure of claim 1, wherein said front left hand rail is offset by atleast 2.5 degrees from said front right hand rail.
 10. The frontstructure of claim 1, wherein said front left hand rail and said frontright hand rail are each comprised of an aluminum extrusion.
 11. Thefront structure of claim 1, wherein said front left hand rail and saidfront right hand rail are each comprised of an aluminum alloy extrusion.12. The front structure of claim 1, wherein said front left hand railand said front right hand rail are each comprised of a steel extrusion.13. The front structure of claim 1, wherein said front left hand railand said front right hand rail each have a cross-sectional height and across-sectional width, wherein said cross-sectional height is at leasttwice said cross-sectional width.
 14. The front structure of claim 1,wherein said front left hand rail and said front right hand rail eachhave a cross-sectional height and a cross-sectional width, wherein saidcross-sectional height is at least 2.5 times said cross-sectional width.15. The front structure of claim 1, wherein said polygonal-shaped upperhollow channel and said polygonal-shaped lower hollow channel of saidfront left hand rail and said polygonal-shaped upper hollow channel andsaid polygonal-shaped lower hollow channel of said front right hand raileach utilize a non-regular, octagon-shaped structure.
 16. The frontstructure of claim 1, wherein said polygonal-shaped upper hollow channeland said polygonal-shaped lower hollow channel of said front left handrail and said polygonal-shaped upper hollow channel and saidpolygonal-shaped lower hollow channel of said front right hand rail eachutilize a regular, octagon-shaped structure.
 17. The front structure ofclaim 1, wherein said polygonal-shaped upper hollow channel and saidpolygonal-shaped lower hollow channel each utilize a non-regular,hexagon-shaped structure.
 18. The front structure of claim 1, whereinsaid polygonal-shaped upper hollow channel and said polygonal-shapedlower hollow channel each utilize a regular, hexagon-shaped structure.19. The front structure of claim 1, further comprising a first crush canand a second crush can, wherein said first crush can is interposedbetween said first end portion of said front left hand rail and saidleft portion of said vehicle bumper, and wherein said second crush canis interposed between said first end portion of said front right handrail and said right portion of said vehicle bumper.
 20. The frontstructure of claim 1, further comprising a front vehicle module, whereina first mounting plate of said front vehicle module is interposedbetween said first end portion of said front left hand rail and saidleft portion of said vehicle bumper, and wherein a second mounting plateof said front vehicle module is interposed between said first endportion of said front right hand rail and said right portion of saidvehicle bumper.